The durability of solid backfilling based on carbonated coal-based waste (CCBW) under mine water environments is critical for its engineering feasibility. This study investigates the deterioration mechanisms of CCBW exposed to acid solution (Acid W), alkaline solution (Alkaline W), and mine water (Mine W) through hydrochemical analysis, XRD, and SEM. Results reveal that the uniaxial compressive strength of CCBW decreased by 10.05, 3.93, and 1.62% after 28 days of immersion in the groups, respectively. Acid conditions induced CaCO₃ dissolution and gypsum formation, while alkaline environments triggered alkali-silica reaction expansion. Mine water exhibited minimal impact due to suspended particles mitigating ion exchange. Carbonation also enhanced the durability of CCBW by forming dense CaCO₃ clusters and C-A-S-H gels, thus reducing ion leaching. Notably, the average erosion resistance of carbonated samples (CCBW-5, 10, 30) was 2.32% higher than that of noncarbonated counterparts. These findings confirm the feasibility of CCBW applications in weakly alkaline mine water and highlight its potential for sustainable coal mining practices, aligning with carbon capture and circular economy principles.

This research introduces a novel dual CO₂ storage (DCS) approach by simultaneously storing CO₂ gas in abandoned mines and securing it within mineralized backfill. For this method, CO₂ mineralized backfill materials (CMBM) are pumped into CO₂ mineralized storage segments (CMSSs) to support the roof while gaseous CO₂ is injected into gaseous CO₂ storage segments (GCSSs) to maximize storage amounts. This study focuses on the Yu-Shen coal area in Yulin City, Shaanxi Province, China. A three-level evaluation model was constructed to predict DCS feasibility based on the analytic hierarchy process (AHP) and fuzzy comprehensive assessment method. The model was generalized and applied to the whole coal area. Each indicator affecting adaptability is plotted on a thematic map to determine the corresponding membership degree. The aptness for 400 boreholes distributed in the entire area was derived and a zoning map which divides the whole area into different suitability was drawn. This paper puts forward a mathematical model for predicting DCS suitability. The findings establish an engineering paradigm that simultaneously addresses CO₂ sequestration, industrial waste recycling, and ecological water table preservation. The research results can provide references for determining the site of DCS, contributing to the generalization of DCS in a larger range.

Synergistic modifiers enhance CO ₂ -carbonated backfill to suppress heavy metal leaching under high-salinity conditions. The immobilization is driven by physical encapsulation, electrostatic attraction, ion exchange, precipitation, and complexation.